Question: Simplify the following expression: $k = \dfrac{7z}{4} - \dfrac{3z}{10}$
In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $10$ $\lcm(4, 10) = 20$ $ k = \dfrac{5}{5} \cdot \dfrac{7z}{4} - \dfrac{2}{2} \cdot \dfrac{3z}{10} $ $k = \dfrac{35z}{20} - \dfrac{6z}{20}$ $k = \dfrac{35z -6z}{20}$ $k = \dfrac{29z}{20}$